{"id": "1222098543096627207", "title": "Tropical Cyclone Discussion", "adv_date": "2026-10-26T15:00:00Z", "msg": "387\nWTPZ42 KNHC 261434\nTCDEP2\n \nTropical Storm Vance Discussion Number  21\nNWS National Hurricane Center Miami FL       EP222026\n900 AM CST Mon Oct 26 2026\n \nVance is experiencing 15 to 20 kt of west-southwesterly vertical\nwind shear.  It appears that the surface center is near the\nwest-southwest edge of the main convective area.  The latest TAFB\nCurrent Intensity number remains 3.5/55 kt.  Recent objective\nintensity estimates from UW-CIMSS have been running in the 45-55 kt\nrange.  The initial intensity is held at 55 kt for this advisory.\n\nVance's estimated motion is west-northwestward or 295/6 kt, aided by \nGPMI and AMSR-3 microwave passes from around 0800 UTC.  This slow \nwest-northwestward track is expected to continue over the next 24 \nhours or so due to a weak mid-level ridge to the north of the \nsystem.  By Wednesday, a broad mid-level trough near the Baja \nCalifornia peninsula should induce a turn toward the north.  The NHC \ntrack forecast has again been shifted to the west of the previous \none, but not as far west as the Google DeepMind Ensemble Mean.  The \nofficial forecast is in good agreement with the latest HFIP \nCorrected Consensus Approach (HCCA).\n\nAlthough Vance remains in a favorable thermodynamic environment with \nwarm water and enough atmospheric moisture, the cyclone is \nexperiencing moderate to strong west-southwesterly wind shear.  The \nwind shear is forecast to increase a bit more (to near 25 kt) over \nthe next 12 to 24 hours, and this should be enough to cause steady \nweakening over the next day or so.  On Wednesday, as Vance turns \nnorthward and gets closer to the broad trough over Baja California \nand the subtropical jet, the west-southwesterly vertical wind shear \nincreases to over 35 kt, and is forecast to increase further on \nThursday.  Surprisingly, most of the models hold onto this system as \na tropical storm for a couple more days.  The NHC forecast is \nslightly lower than the previous forecast, and lies in the middle of \nthe guidance envelope through 48 hours, near the HCCA model.  From \n60 hours onward, the NHC intensity forecast is near the lower end of \nthe model guidance suite, near the average of the GDMI and HCCA \nmodels.  It is likely that Vance's convection will be sheared off by \n72 hours, and the new forecast has moved up post-tropical timing to \nthis period.  Nearly all of the models show the circulation \ndissipating by day 5, so the NHC forecast shows dissipation by this \ntime, just before it reaches the coast of Mexico.\n\n \nKey Messages:\n\n1. Periods of heavy rainfall associated with Vance will impact \nportions of western Mexico during much of this week. This rainfall \nmay produce flooding and mudslides across southern Sinaloa, \nsouthwest Durango and coastal sections of Nayarit, Jalisco, Colima \nand Michoacan, especially in areas along steep terrain.\n\n2. Although the wind threat to southwest Mexico is decreasing as the\nforecast track shifts westward away from the coast, interests there\nshould continue to monitor Vance's progress.\n \n \nFORECAST POSITIONS AND MAX WINDS\n \nINIT  26/1500Z 15.4N 105.7W   55 KT  65 MPH\n 12H  27/0000Z 15.7N 106.6W   45 KT  50 MPH\n 24H  27/1200Z 16.4N 107.6W   40 KT  45 MPH\n 36H  28/0000Z 17.6N 108.2W   40 KT  45 MPH\n 48H  28/1200Z 19.2N 108.4W   40 KT  45 MPH\n 60H  29/0000Z 20.7N 108.4W   35 KT  40 MPH\n 72H  29/1200Z 22.0N 108.2W   30 KT  35 MPH...POST-TROP/REMNT LOW\n 96H  30/1200Z 24.1N 108.0W   25 KT  30 MPH...POST-TROP/REMNT LOW\n120H  31/1200Z...DISSIPATED\n \n"}